The present invention relates to a method of updating a layout of circuit elements on a semiconductor integrated circuit or on a printed circuit board (hereinafter referred to as a substrate), and more particularly, to a layout updating method suitable for modifying the layout of the circuit elements on the semiconductor integrated circuit by an interactive operation.
In a layout method concerning layout and wiring methods for instance, see p1164.about.p1171 of a treatise issued in 1983, Vol. J66-C, No. 12, published by Institute of Electronics and Communication Engineers of Japan), wherein logical circuit elements are disposed on a substrate and signal wires between terminals of the elements are connected in accordance with an orthogonal wiring method in which a first wiring operation is carried out in the lateral direction and a second wiring operation is executed in the perpendicular direction, it is in general required that the wiring length not exceed a specified value, depending on the driving capability of the logical circuit elements. Namely, if an aggregate of the logical circuit elements linked to a single signal line is disposed in an extraordinarily broad range, the situation will transcend the limits of placement constraint.
According to a layout updating method for especially renewing the placement of the logical circuit elements disposed on the substrate, it is feasible to display configurations of the logical circuit elements, arrangement positions thereof and empty areas as well where no element is disposed. It is therefore practicable that the logical circuit elements are replaced or shifted, and an aggregate of the elements linked to a given signal line is classified by color and connected by line segments in order to be displayed.
While on the other hand, a layout updating method that has heretofore been adopted creates such defects that if the aggregate of the logical circuit elements linked to a predetermined signal line is modified in terms of layout, while maintaining the placement constraint, it is inexplicit to select the elements which are to be shifted or replaced, and to specify the destinations to which the elements are moved, this tending to require a longer time than expected in settling the final placement which meets the placement constraint thereof on account of the user's tendency to rely on trial and error evaluation which is based on his intuition.